Engagement features and adjustment structures for electronic devices with integral antennas

ABSTRACT

Electronic devices may be provided that contain wireless communications circuitry. The wireless communications circuitry may include antenna structures that are formed from an internal ground plane and a peripheral conductive housing member. The internal ground plane and peripheral conductive housing member may be separated by a gap. The internal ground plane may be formed from sheet metal structures having engagement features such as tabs bent upwards at an angle. Plastic structures may be insert molded over the engagement features. When the internal ground plane is mounted in the electronic device, the plastic structures may bridge the gap between the internal ground plane and the peripheral conductive housing member. An adjustable structure such as a washer with a selectable thickness may be mounted to the peripheral conductive housing member opposing conductive structures across the gap. The thickness may be adjusted to adjust antenna performance.

This application claims the benefit of provisional patent applicationNo. 61/431,523, filed Jan. 11, 2011, which is hereby incorporated byreference herein in its entirety.

BACKGROUND

This relates generally to electronic devices, and, more particularly, tohousing structures and adjustable antenna structures for electronicdevices.

Electronic devices such as cellular telephones and other devices oftencontain wireless communications circuitry. The wireless communicationscircuitry may include, for example, cellular telephone transceivercircuits for communicating with cellular telephone networks. Wirelesscommunications circuitry in an electronic device may also includewireless local area network circuits and other wireless circuits.Antenna structures are used in transmitting and receiving wirelesssignals.

To satisfy consumer demand for small form factor wireless devices,manufacturers are continually striving to implement wirelesscommunications circuitry such as antennas using compact arrangements. Atthe same time, it may be desirable to include conductive structures inan electronic device such as metal device housing components. Becauseconductive components can affect radio-frequency performance, care mustbe taken when incorporating antennas into an electronic device thatincludes conductive structures. In some arrangements, it may bedesirable to use conductive housing structures in forming antennastructures for a device. Such antenna structures may be sensitive to thelayout of conductive housing structures. Locating the conductive housingstructures and associated components within an electronic device withoutadversely impacting antenna performance can therefore pose challenges.

It would therefore be desirable to be able to provide improvedarrangements for adjusting and mounting structures within an electronicdevice that are associated with antenna performance.

SUMMARY

Electronic devices may be provided that contain wireless communicationscircuitry. The wireless communications circuitry may include antennastructures that are formed from a ground plane and a peripheralconductive housing member. The ground plane and peripheral conductivehousing member may be separated by a gap. The gap may be filled withdielectrics such as air and plastic. Conductive components along theedges of the gap may influence the layout of the gap and therebyinfluence antenna performance.

The ground plane may be formed from sheet metal structures havingprotruding engagement features such as tabs bent upwards at an angle.Plastic structures may be insert molded over the engagement features.The tabs may be bent at a 45° angle and may be provided with dovetailedprofiles to resist separation between the plastic structures and thesheet metal structures. When the ground plane is mounted in theelectronic device, the plastic structures may bridge the dielectric gapbetween the internal ground plane and the peripheral conductive housingmember.

An adjustable structure such as a washer or other member with aselectable thickness may be mounted to the peripheral conductive housingmember across the gap from conductive structures such as camerastructures that are associated with the ground plane. If tests duringmanufacturing reveal that antenna performance is deviating from desiredcriteria, the thickness of the adjustable structure may be adjusted totune antenna performance.

Further features of the invention, its nature and various advantageswill be more apparent from the accompanying drawings and the followingdetailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an illustrative electronic device of thetype that may be provided with antenna structures that are formed usinghousing structures in accordance with an embodiment of the presentinvention.

FIG. 2 is a top interior view of an electronic device of the type shownin FIG. 1 in accordance with an embodiment of the present invention.

FIG. 3 is a diagram showing where gaps between conductive electronicdevice housing structures may be formed to form antenna structures inaccordance with an embodiment of the present invention.

FIG. 4 is a side view of conductive internal housing structures such asground plane structures showing how the ground plane structures may beprovided with engagement features that help in attaching a dielectricstructure in accordance with an embodiment of the present invention.

FIG. 5 is a diagram showing an illustrative dovetail shape that may beused for the engagement features of FIG. 4 in accordance with anembodiment of the present invention.

FIG. 6 is a perspective view of a portion of an electronic deviceincluding the features of FIG. 5 in accordance with an embodiment of thepresent invention.

FIG. 7 is a perspective view of the portion the electronic device ofFIG. 6 in which a dielectric structure such as an insert-molded plasticmember has been attached to the engagement features on the ground platestructures in accordance with an embodiment of the present invention.

FIG. 8 is a top view of an interior corner portion of an electronicdevice in the vicinity of a gap region used as part of an antennashowing how the corner of the device may be provided with an adjustableconductive structure for making antenna adjustments in accordance withan embodiment of the present invention.

FIG. 9 is an exploded perspective view of the interior electronic deviceportion of FIG. 8 showing how the adjustable conductive structures mayinclude a washer or other conductive member with a thickness that may beselected to make antenna adjustments in accordance with an embodiment ofthe present invention.

FIG. 10 is a perspective view of the interior of the electronic deviceof FIG. 9 showing how the adjustable conductive structures may opposeconductive device components across an antenna gap region in accordancewith an embodiment of the present invention.

DETAILED DESCRIPTION

Electronic devices may be provided with wireless communicationscircuitry. The wireless communications circuitry may be used to supportwireless communications in one or more wireless communications bands.Antenna structures in an electronic device may be used in transmittingand receiving radio-frequency signals.

An illustrative electronic device that contains wireless communicationscircuitry is shown in FIG. 1. Device 10 of FIG. 1 may be a notebookcomputer, a tablet computer, a computer monitor with an integratedcomputer, a desktop computer, or other electronic equipment. If desired,electronic device 10 may be a portable device such as a cellulartelephone, a media player, other handheld devices, a wrist-watch device,a pendant device, an earpiece device, or other compact portable device.

As shown in FIG. 1, device 10 may have a housing such as housing 11.Housing 11 may be formed from materials such as plastic, metal, carbonfiber and other fiber composites, ceramic, glass, wood, other materials,or combinations of these materials. Device 10 may be formed using aunibody construction in which some or all of housing 11 is formed from asingle piece of material (e.g., a single cast or machined piece ofmetal, a single piece of molded plastic, etc.) or may be formed fromframe structures, housing sidewall structures, and other structures thatare assembled together using fasteners, adhesive, and other attachmentmechanisms. In the illustrative arrangement shown in FIG. 1, housing 11includes conductive peripheral housing member 12. Conductive peripheralhousing member 12 may have a ring shape that runs around the rectangularperiphery of device 10. One or more gaps such as gaps 30 may be formedin conductive peripheral housing member 12. Gaps such as gaps 30 may befilled with dielectric such as plastic and may interrupt the otherwisecontinuous shape of conductive peripheral housing member. Conductiveperipheral housing member may have any suitable number of gaps 30 (e.g.,more than one, more than two, three or more, less than three, etc.).

Conductive peripheral housing member 12 may be formed from a durablematerial such as metal. Stainless steel may be used for forming housingmember 12 because stainless steel is aesthetically appealing, strong,and can be machined during manufacturing. Other metals may be used ifdesired. The rear face of housing 11 may be formed from plastic, glass,metal, ceramic composites, or other suitable materials. For example, therear face of housing 11 may be formed form a plate of glass havingregions that are backed by a layer of internal metal for added strength.Conductive peripheral housing member 12 may be relatively short invertical dimension Z (e.g., to serve as a bezel for display 14) or maybe taller (e.g., to serve as the sidewalls of housing 11 as shown in theillustrative arrangement of FIG. 1).

Device 10 may include components such as buttons, input-output portconnectors, ports for removable media, sensors, microphones, speakers,status indicators, and other device components. As shown in FIG. 1, forexample, device 10 may include buttons such as menu button 16. Device 10may also include a speaker port such as speaker port 18 (e.g., to serveas an ear speaker for device 10).

One or more antennas may be formed in device 10. The antennas may, forexample, be formed in locations such as locations 24 and 26 to provideseparation from the conductive elements of display 14. Antennas may beformed using single band and multiband antenna structures. Examples ofcommunications bands that may be covered by the antennas includecellular telephone bands (e.g., the bands at 850 MHz, 900 MHz, 1800 MHz,1900 MHz, and 2100 MHz), satellite navigation bands (e.g., the GlobalPositioning System band at 1575 MHz), wireless local area network bandssuch as the IEEE 802.11 (WiFi®) bands at 2.4 GHz and 5 GHz, theBluetooth band at 2.4 GHz, etc. Examples of antenna configurations thatmay be used for the antennas in device 10 include monopole antennas,dipole antennas, strip antennas, patch antennas, inverted-F antennas,coil antennas, planar inverted-F antennas, open slot antennas, closedslot antennas, loop antennas, hybrid antennas that include antennastructures of multiple types, or other suitable antenna structures.

Device 10 may include one or more displays such as display 14. Display14 may be a liquid crystal display (LCD), an organic light-emittingdiode (OLED) display, a plasma display, an electronic ink display, etc.A touch sensor may be incorporated into display 14 (i.e., display 14 maybe a touch screen). The touch sensor may be an acoustic touch sensor, aresistive touch sensor, a piezoelectric touch sensor, a capacitive touchsensor (e.g., a touch sensor based on an array of indium tin oxidecapacitor electrodes), or a touch sensor based on other touchtechnologies.

Display 14 may be covered by a transparent planar conductive member suchas a layer of glass or plastic. The cover layer for display 14, which issometimes referred to as a cover glass layer or cover glass, may extendover substantially all of the front face of device 10, as shown inFIG. 1. The rectangular center portion of the cover glass (surrounded bydashed line 20 in FIG. 1) contains an array of image pixels and issometimes referred to as the active portion of the display. Theperipheral outer portion of the cover glass (i.e., rectangularperipheral ring 22 of FIG. 1) does not contain any active image pixelsand is sometimes referred to as the inactive portion of display 14. Apatterned opaque masking layer such as a peripheral ring of black inkmay be formed under inactive portion 22 to hide interior devicecomponents from view by a user.

FIG. 2 is a top view of the interior of device 10 showing how antennas40L and 40U may be implemented within housing 12. As shown in FIG. 2,ground plane G may be formed within housing 12. Ground plane G may formantenna ground for antennas 40L and 40U. Because ground plane G mayserve as antenna ground, ground plane G may sometimes be referred to asantenna ground, ground, or a ground plane element (as examples). One ormore printed circuit boards or other mounting structures may be used tomount components 31 in device 10. Components 31 may includeradio-frequency transceiver circuits that are coupled to antennas 40Uand 40L using transmission lines 52L and 52U, processors,application-specific integrated circuits, cameras, sensors, switches,connectors, buttons, and other electronic device components.

In central portion C of device 10, ground plane G may be formed byconductive structures such as a conductive housing midplate member(sometimes referred to as an internal housing plate or planer internalhousing structures). The structures of ground plane G may be connectedbetween the left and right edges of member 12. Printed circuit boardswith conductive ground traces (e.g., one or more printed circuit boardsused to mount components 31) may form part of ground plane G.

The midplate member may have one or more individual sections (e.g.,patterned sheet metal sections) that are welded together. Portions ofthe midplate structures may be covered with insert-molded plastic (e.g.,to provide structural support in portions of the interior of devicewhere no conductive ground is desired, such dielectric-filled portionsof antennas 40U and 40L in regions 24 and 26).

At ends 24 and 26 of device 10, the shape of ground plane G may bedetermined by the shapes and locations of conductive structures that aretied to ground. Ground plane G in the simplified layout of FIG. 2 has astraight upper edge UE and a straight lower edge LE. In actual devices,the upper and lower edges of ground plane G and the interior surface ofconductive peripheral housing member 12 generally have more complexshapes determined by the shapes of individual conductive structures thatare present in device 10. Examples of conductive structures that mayoverlap to form ground plane G and that may influence the shape of theinner surface of member 12 include housing structures (e.g., aconductive housing midplate structure, which may have protrudingportions), conductive components (e.g., switches, cameras, dataconnectors, printed circuits such as flex circuits and rigid printedcircuit boards, radio-frequency shielding cans, buttons and conductivebutton mounting structures), and other conductive structures in device10. In the illustrative layout of FIG. 2, the portions of device 10 thatare conductive and tied to ground to form part of ground plane G areshaded and are contiguous with central portion C.

Openings such as openings 138 and 140 (sometimes referred to as gaps)may be formed between ground plane G and respective portions ofperipheral conductive housing member 12. Openings 138 and 140 may befilled with air, plastic, and other dielectrics. Openings 138 and 140may be associated with antenna structures 40U and 40L.

Lower antenna 40L may be formed by a loop antenna structure having ashape that is determined at least partly by the shape of the lowerportions of ground plane G and conductive housing member 12. In theexample of FIG. 2, opening 138 is depicted as being rectangular, butthis is merely illustrative. In practice, the shape of opening 138 maybe dictated by the placement of conductive structures in region 26 suchas a microphone, flex circuit traces, a data port connector, buttons, aspeaker, etc.

Lower antenna 40L may be fed using an antenna feed made up of positiveantenna feed terminal 58L and ground antenna feed terminal 54L.Transmission line 52L may be coupled to the antenna feed for lowerantenna 40L. Gap 30′ may form a capacitance that helps configure thefrequency response of antenna 40L. If desired, device 10 may haveconductive housing portions, matching circuit elements, and otherstructures and components that help match the impedance of transmissionline 52L to antenna 40L.

Antenna 40U may be a two-branch inverted-F antenna. Transmission line52U may be used to feed antenna 40U at antenna feed terminals 58U and54U. Conductive structures 150 may form a shorting path that bridgesdielectric opening 140 and electrically shorts ground plane G toperipheral housing member 12. Conductive structure 148 (which may beformed using structures of the type used in forming structures 150 orother suitable structures) and matching circuit M may be used to connectantenna feed terminal 58U to peripheral conductive member 12 at point152. Conductive structures such as structures 148 and 150 (which aresometimes referred to as conductive paths) may be formed by flex circuittraces, conductive housing structures, springs, screws, weldedconnections, solder joints, brackets, metal plates, or other conductivestructures.

Gaps such as gaps 30′, 30″, and 30′″ (e.g., gaps 30 of FIG. 1) may bepresent in peripheral conductive member 12. A phantom gap may beprovided in the lower right-hand portion of device 10 for aestheticsymmetry if desired. The presence of gaps 30′, 30″, and 30′″ may divideperipheral conductive housing member 12 into segments. As shown in FIG.2, peripheral conductive member 12 may include first segment 12-1,second segment 12-2, and third segment 12-3.

Segment 12-1 may form antenna resonating element arms for antenna 40U.In particular, a first portion (segment) of segment 12-1 may extend frompoint 152 (where segment 12-1 is fed) to the end of segment 12-1 that isdefined by gap 30″ and a second portion (segment) of segment 12-1 mayextend from point 152 to the opposing end of segment 12-1 that isdefined by gap 30′″. The first and second portions of segment 12-1 mayform respective branches of an inverted F antenna and may be associatedwith respective low band (LB) and high band (HB) antenna resonances forantenna 40U. The relative positions of structures 148 and 150 along thelength of member 12-1 may affect the response of antenna 40U and may beselected to tune antenna 40U. Antenna tuning adjustments may also bemade by adjusting matching circuit M, by adjusting the configuration ofcomponents used in forming paths 148 and 150, by adjusting the shapes ofopening 140, etc. Antenna 40L may likewise be adjusted.

With one illustrative arrangement, antenna 40L may cover the transmitand receive sub-bands in five communications bands (e.g., 850 MHz, 900MHz, 1800 MHz, 1900 MHz, and 2100 MHz). Antenna 40U may, as an example,be configured to cover a subset of these five illustrativecommunications bands. For example, antenna 40U may be configured tocover a two receive bands of interest and, with tuning, four receivebands of interest.

Proper functioning of antennas 40L and 40U relies, at least partly, onthe presence of gaps 138 and 140. The size and shape of gaps 138 and 140is determined by the placement of housing structures such as peripheralconductive housing member 12 and the conductive structures of groundplane G and by conductive component structures that line the interior ofgap G. To preserve the presence of gaps 138 and 140 while providingstructural support for ground plane G in regions 24 and 26, it may bedesirable to add dielectric support structures to the ends of groundplane G, such as dielectric structures 160. Structures 160 may, forexample, be formed from injection-molded (insert-molded) plastic.Because structures 160 are formed from dielectric, the shape of opening140 (in the FIG. 3 example) is not altered by the presence of structures160. Structures 160 may, however, help to provide support for the upperend of ground plane G (e.g., by helping to attach edge UE to theinterior portions of peripheral conductive housing member 12). With onesuitable arrangement, the structures of ground plane G may be formedfrom multiple sheet metal (e.g., stainless steel) sections that areattached to each other using welds and overmolded plastic. Structures160 may be injection molded over the upper portions of ground plane Gand may have portions that fit within one or more recesses in peripheralconductive housing member 12.

To ensure that the joint between structures 160 and the metal sheetstructures of ground plane G is sufficiently robust, it may be desirableto form engagement features on the edge of ground plane G. Theseengagement features may take the form of bent metal protrusions (as anexample).

An illustrative arrangement in which ground plane G is provided withbent metal prongs that serve as engagement features for polymerstructures 160 is shown in FIG. 4. As shown in the cross-sectional viewof FIG. 4, engagement features 162 may be formed by bending patternedprotruding portions of the edge of ground plane G at an angle θ relativeto the plane of ground plane G. The angle θ may be, for example, about45° (e.g., 20 to 60° or other suitable non-zero angle). With this typeof configuration, engagement features 162 may resist detachment fromground plane G in both dimension Z (i.e., parallel to the surface normalto the plane of ground plane G) and dimension Y (parallel to thelongitudinal axis of device 20 and ground plane G).

To help prevent structures 160 from pulling away from engagementstructures 162, engagement structures 162 may be provided with adovetail shape of the type shown in FIG. 5. Other shapes that helpcapture part of structures 160 and thereby resist removal of structures160 from ground plane G may be used if desired. The illustrativeprofiles of the bent dovetail-shaped tabs that form engagementstructures 162 of FIG. 5 are merely illustrative.

FIG. 6 is a perspective view of an interior portion of device 10 in thevicinity of engagement structures 162 on ground plane G in whichstructures 160 have been omitted to allow engagement feature 162 to beviewed. As shown in FIG. 6, peripheral conductive housing member 12 mayhave portions such as recessed portion 164 that receive mating edgeportions of member 160. This helps secure member 160 and thereforeground plane G within housing 11.

FIG. 7 is a perspective view of the interior portion of device 10 ofFIG. 6 in which structures 160 have been included. As shown in FIG. 7,structures 160 provide a dielectric mechanical support that bridges gap140 without imposing conductive structures within gap 140.

To ensure that antennas such as antenna 40U and 40L perform properly, itis sometimes desirable to provide adjustable components in device 10. Iftesting reveals that antenna performance should be altered, theconfiguration of the adjustable components can be changed duringmanufacturing to ensure that device 10 is manufactured according todesign specifications.

FIG. 8 is a top view of an illustrative antenna tuning structure of thetype that may be used in device 10. In the example of FIG. 8, adjustablestructure 166 has been formed in antenna 40U in region 24. This ismerely illustrative. Any antenna structures may be provided withadjustable components such as adjustable structure 166 if desired. Asshown in FIG. 8, the shape of opening 140 may be partly determined bythe locations of components that include conductive portions such ascomponent 172. Component 172 may be, for example, a camera module.

Adjustable structure 166 may be formed from conductive structures thatinfluence the size and shape of opening 140. In some configurations,structure 166 has a relatively shallow height H, reaching surface 168.In other configurations, structure 166 has a large height H (e.g., sothat the outermost surface of structure 166 is aligned with dashed line170). The location of the surface of structure 166 influences theelectrical performance of antenna 40L (e.g., by changing the shape ofopening 140, by changing capacitances in antenna 40U such as the shuntcapacitance between conductive peripheral housing member 12 and groundplane G that is influenced by the distance D between member 12 andcomponent 172 in the vicinity of structure 166, etc.).

During manufacturing, the performance of antenna structures such asantenna 40U may be measured. If the performance of antenna 40U needs tobe adjusted, corresponding adjustments to the value of height H may bemade to adjustable structure 166. Once the performance of one or moresample devices has been characterized in this way, subsequent devices ofthe same configuration (e.g., devices that include peripheral conductivehousing members, and ground plane structures G from common sources andthat are manufactured using the same techniques), can be similarlyadjusted. This type of adjustment may therefore be made to numerousdevices on a production line, without needing to individuallyremanufacture components such as peripheral conductive housing member 12or ground plane G.

With one illustrative arrangement, adjustable structure 166 includes awasher or other suitable shim and a screw that are mounted to a threadedstructure on peripheral conductive housing member 12. FIG. 9 is anexploded perspective view of device 10 showing how adjustable structure166 may include screw 172 and metal washer 174. Dashed line 177 showsthe edge of ground plane G in the vicinity of washer 174. Acorresponding assembled view is shown in FIG. 10.

The foregoing is merely illustrative of the principles of this inventionand various modifications can be made by those skilled in the artwithout departing from the scope and spirit of the invention.

What is claimed is:
 1. An electronic device, comprising: a housinghaving conductive structures that form an antenna ground for an antennaand having a peripheral conductive member that runs around at least someedges of the housing and forms at least part of the antenna, wherein theantenna ground and the peripheral conductive member are separated by agap and wherein the conductive structures have protruding engagementfeatures; and a plastic structure in the gap that is molded over theprotruding engagement features.
 2. The electronic device defined inclaim 1 wherein the plastic structure bridges the gap and contacts theperipheral conductive member, wherein the conductive structures compriseat least one internal sheet metal structure, and wherein the protrudingengagement features comprises bent tabs.
 3. The electronic devicedefined in claim 2 wherein the bent tabs have profiles that resistseparation between the plastic structure and the conductive structures.4. The electronic device defined in claim 3 wherein the bent tabs havedovetailed profiles.
 5. The electronic device defined in claim 3 whereinthe internal sheet metal structure lies in a plane and wherein the benttabs are bent at an angle of 20° to 60° with respect to the plane. 6.The electronic device defined in claim 2 wherein the housing has arectangular periphery and wherein the peripheral conductive membercomprises a metal housing member that forms sidewalls for the housingand that extends around the rectangular periphery.
 7. The electronicdevice defined in claim 6 further comprising: radio-frequencytransceiver circuitry that transmits and receives radio-frequencyantenna signals through the antenna.
 8. The electronic device defined inclaim 1 wherein the peripheral conductive member and the conductivestructures comprise stainless steel.
 9. An electronic device,comprising: a housing containing conductive structures that form anantenna ground for an antenna and having a peripheral conductive memberthat runs around at least some edges of the housing and forms at leastpart of the antenna, wherein the antenna ground and the peripheralconductive member are separated by a gap; and an adjustable conductivestructure on the peripheral conductive member that is configured to tunethe antenna by adjusting the gap.
 10. The electronic device defined inclaim 9 wherein the adjustable conductive structure comprises: a screw;and a washer that is held to the peripheral conductive member by thescrew.
 11. The electronic device defined in claim 10 wherein theconductive structures that form the antenna ground comprise a camera.12. The electronic device defined in claim 11 wherein the camera andwasher are separated from each other by the gap.
 13. The electronicdevice defined in claim 9 wherein the conductive structures that formthe antenna ground include at least one layer of sheet metal.
 14. Theelectronic device defined in claim 13 wherein the peripheral conductivemember comprises a ring-shaped stainless steel member.
 15. Theelectronic device defined in claim 14 further comprising plastic in thegap.
 16. An electronic device comprising: ground plane conductivestructures having engagement features; a rectangular ring-shapedperipheral conductive housing member having a portion that is separatedfrom the ground plane conductive structures by a gap; at least oneplastic structure in the gap that is attached to the engagementfeatures; and an adjustable conductive structure on the portion of therectangular ring-shaped peripheral conductive housing member.
 17. Theelectronic device defined in claim 16 wherein the ground planeconductive structures comprise sheet metal and wherein the engagementfeatures comprise tabs that protrude from the sheet metal.
 18. Theelectronic device defined in claim 17 wherein the adjustable conductivestructure comprises a metal member with a thickness selected to modify adimension associated with part of the gap.
 19. The electronic devicedefined in claim 18 wherein the ground plane conductive structures andrectangular ring-shaped peripheral conductive housing member form partof at least one antenna, the electronic device further comprising aradio-frequency transceiver coupled to the antenna.
 20. The electronicdevice defined in claim 19 wherein the metal member comprises a washer,wherein the adjustable conductive structure includes a screw thatattaches the washer to the rectangular ring-shaped peripheral conductivehousing member, wherein the tabs comprise bent tabs, and wherein theplastic structure comprises plastic that is molded over the bent tabs.